Vehicle interior panels typically include a decorative aspect, providing the passenger cabin of a vehicle with a desired aesthetic. Combinations of different types of materials, textures, shapes, tactile features, and visual features can be used with such panels to provide the passenger cabin with any of a variety of different ambiences, from luxurious to utilitarian. Modern materials can be shaped into complex contoured shapes and are used extensively in vehicle interiors due to the available design freedom. For example, plastic injection molding can be used to shape polymer-based materials into nearly any three-dimensional shape in a single process, and thermoforming can be used to shape a polymer-based sheet material to include nearly any three-dimensional contour. As vehicle interior designers seek to differentiate their products from others, certain limitations of these materials and processes have come to light. For instance, thermoforming processes stretch the sheet material being formed, and the sheet material can only stretch so far before breaking or otherwise losing integrity.
Japanese publication JPS59232816 by Masamichi et al. discloses a thermoforming process in which an excess material portion is provided in advance of the thermoforming process to reinforce a particular portion of the formed material to have the desired strength in the finished product, such as an armrest.